Abstract
TMBP200 of tobacco BY-2 cells is a member of the highly conserved family of microtubule associated proteins including Xenopus MAP215, Human TOGp and Arabidopsis MOR1/GEM1. We generated some mutant BY-2 cell lines in which TMBP200 is conditionally downregulated by inducible expression of RNA interference (RNAi) constructs. Depletion of TMBP200 caused an appearance of multinucleated cells in a high frequency due to the severe disorganization of spindle and phragmoplast microtubule arrays. In interphase cells, RNAi depletion of TMBP200 did not cause severe effects on cortical microtubules (cMTs) such as fragmentation and depolymerization. In TMBP200 depleted cells as well as control cells cMTs were recovered from propyzamide-induced depolymerization after the termination of the propyzamide treatment. However, depletion of TMBP200 inhibited the cytokinin-induced elongation of protoplast-derived cells, suggesting that TMBP200 have an important role in cMT reorganization during cell elongation.
